A lens cover includes a cap adapted to be pivotably supported on an optical device. A stop may be positioned to interfere with spring-driven movement of the cap and to brake the cap at an intermediate position between closed and open positions thereof, and to allow the cap to be manually moved to the fully open position. An optional detent structure is disclosed for releasably retaining the cap in its open position. A mounting ring assembly of the lens cover may include a first threaded ring member for attachment to the optical device and a second ring member rotatably coupled to the first ring member for positioning a hinge that pivotably attaches the cap to the second ring member. Magnets may be included to retain the cap in the closed position. The mounting ring assembly, the cap, or both may be formed of a metal such as aluminum.